With the rapid development of electronic technologies, electronic devices such as mobile phones, tablets, and computers are more widely applied to people's daily study, work, and lives. In using an electronic device, the screen is a major means through which people acquire various information. However, in conventional techniques, various information includes some personal privacy-related sensitive information, which is generally presented on the screen directly and is easily spied by other people, causing leakage of personal information and bringing about unnecessary trouble to people's life.